Abstract

We report that a very thin film of titania, with thickness controlled to the order of its Debye length, exhibits reversible on/off electrical switching effects upon hydrogen/air exposure at room temperature. Such extreme changes in electrical conduction are Usually observed only in the "nanosensors" made of their nanoscaled counterparts. The nanofilm of titania with compact, "monograin-equivalent" film structure is fabricated by atomic layer deposition (ALD) with atomic layer control over its thickness. For the first time, the switching effects of the titania nanofilm capped with catalytic Pd nanoparticles are in situ observed with conducting atomic force microscopy (C-AFM) technique. We further demonstrate that the switching effects can be achieved only when the thickness of the nanofilm is reduced to less than 15 nm. In addition, arrays of TiO2 nanowires are fabricated to demonstrate the compatibility of ALD with the planar technology.